Airplane spotter



-c. sAmowsKY AIRPLANE SPOTTER Filed sept. 7. 1942 Nov. 9, 1943.

5 Sheets-Sheet l CHQLES 5,40

5 Sheets-Sheet 2 C. SADOWSKY AIRPLANE SPOTTER Filed Sept. '7, 1942 OHQLE s 64 Nov. 9, 1943. y

Nov. 9, 1943. c. sADowsKY AIRPLANE SPOTTER Filed sept. 7, 1942 3 Sheets-Sheet 3 /Ar ve N rol? CHA @L E s 014D ,f4/JK Y 4v N, l

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Patented Nov. 9, 1943 UNITED STATES PATENT 'OFFICE- AIRPLANE sro'r'riia Charles Sadowsky, New York, N.'Y. Application september 7,1942, lseraienterarse? (o1. 33-71) (Granted under the act of March 3, 1883, as amended April 30, 1928; 3170 0. Gr. 757).

12 Claims.

The invention. described herein may be manufactured andused by or for Government for govemmen-tal. purposes, without the payment to me ofi any royalty thereon.

This invention relates to measuring instruments, and particularly toan instrument for use in estimating the altitude of' an airplane in ilight and' its distance from the observer; and, preferably, also for giving its direction or compass bearing, with respect to the observer at the time the airplane is sighted thro-ugh the instrument.

The principal object of the invention is to provide, in a single simple instrument means for aiding anobserver to estimate both the altitude and' distance of anairplane in flight;y and a further objfect is to include means operated by the sighting of the instrument for giving the direction of the sighted airplane. with respect to the observer.

The invention comprises the assembled cooperating., means hereinafter described, and illustrated in the accompanying drawings. showing a preferred embodiment thereof and a modification and in which:

Fig. 1 is a `side elevation, partly in section, .showingY an airplane spotting instrument or estimator embodying; the invention;r

Fig. 2 is a vertical transverse sectional View taken on'lineT-Z'of Fig. 1,; i,

Fig. 3 isa fragmentary View showing on an enlarged scale a different position ofthe parts of the scissorsbar gauge "mechanism of, Fig. 2;

Fig-,4 is a side elevation of the instrument of Fig. l showing theA parts thereof in one operative or spotting position;

Fig. 5 is a top` plan lview of the direction indicator'of I' and 4; and i Fig. G, is a. perspective view of the gaugeactuated indicator plate, bearing the curve or series of curvesby which the `observer reads the instrument to estimate both distance and altitude.

'lf is a viewinside elevation', partly in section, of ian airplane spotting instrument embodying the invention and vprovided with a modiiield casing and instrument support? Fig; 8 is horizontal vsectional View taken on line 8--8 of Fig; 7`;

9L is aV fragmentary verticalssectional View, on enlarged scalegtafken one line- S--Sll of Fig. 8;

1d is: afragnfientaryl vertical sectional View takenV on line t0 l-il of Fig. 8:. and

Fig. 1l.4 is a horizontal. sectional view through the support taken on. line, H I l of Fig.. 7.

Referringrst particularly to Figs. 1 and 4, the instrument is provided'with a support in the form of a handle H, which includes thetwo spaced plates i3 and l5, between which' depends the pendulum Il vof the scale plate I9 pivotally mountedon the handle' at 2I`. A counterweight 23 xed to the bottomv ofA the pendulum insures that the scale plate l 9 will remain in the position of Figspl an'dl during sighting operation of the instrument as hereinafter described;

vThe scale plate t9 is madeo transparent material,`, andjis` marked off horizontally into height zones as shown in Figs. 1 and'4. These zones'may conveniently beY the commonly accepted altitude zones customarily referred to by airplane spotters in estimating the altitude of a plane in flight as very high,.high, lowand Very low. In accepted standard practice the very low zone is from 0 to 3,000 feet, the low zone from 3,000 to 9,000 feet, the high zone from 9,000 to 17,000 feet and the very high zone Afrom 17,000 to 25,000 feet and higher, and the scale plate i9 is accordingly shown, as being so marked.

, In addition tobeing marked oiT by horizontal lines into height zones the transparent scale plate i9 is marked 01T vertically at equal intervals into distance zones, these vertical lines corresponding to distances, in the present example, of one, two, three, four and ve miles. Thev equal intervals 4betweenany two adjacent lines preserves facility of distance estimation as the distance of the sighted airplane increases.

A reading plate 29, (Figs. l, 2 and 4), preferably opaque, is secured to the outside face of handle plate I5, in 'fixed relation thereto, and is provided. with the narrow reading slot 3| extending horizontally therea'cross as viewed in Fig. 1, this slot being, visible through the pivoted transparent scale plate I 9.

Fixed' to the outer face of the reading plate 29 is a small casingor housing 35, in the upper portion of Awhich is rotatably mounted a gauge actuating shaft 31 whose ends project from the casing. The outer end of the shaft has fixed to it a knurled knob 39, by which the shaft may be manually rotatedthrough a limited angle. The inner end of the shaft 31' has fixed to it an indicator plate 4i (Fig. 6) so that Whatever rotative movement isV imparted toy theknob Will be communicated to the indicator plate, which will thereby be given an eoual angular movement.

To an observer' looking at the face of the instrument shown in Fig. l the portion of' the indicator plate di exposed* byv reading slot 3l will be visible through the transparent scale'plate l0'. fin indicator curve is plottdfontheindicator plate 4H, and that portion of it opposite the reading slot 3| will be visible to the observer, who can then make a distance and altitude estimation reading on the scale plate according to the position Where he sees the plotted curve through the reading slot, as hereinafter described.

Angular movement of the indicator plate itself, and consequently of theplotted curve, is dependent on and co-extensive with the angular movement imparted manually to the knurled knob 39, and in the operation of the instrument the knob is given a rotative angular movementy in one direction or the other to move toward or VawayV from each other a pair of gauge wires' until the sighted plane is exactly included between them.

For the purpose of facilitating this operation, the instrument includes a telescope 45 carried in the housing 35, within whose field of view are two gauge wires 49 and 50 (Figs. 2 and 3) movable toward and away from each other. Each gauge wire is carried by one of a pair of scissors bars 52, whose lowerends are pivotally mounted in the bottom of the casing 35, The upper end of each bar carries a pin 53, by means of which the gauge shaft `imparts movement to -the scissors bars.

The central enlarged portion of shaft 31, located within the casing 35, is provided with a pair of oppositely threaded pin grooves 55 and 56, extending in opposite directions from its center, and each groove receives one of the pins 53. A coil spring 59vunder tension connects the two scissors bars, and acts to urge the scissors bars, and consequently the gauge wires 49 and 50, constantly toward each other. This construction eliminates lost motion of the scissors bar pins in their grooves, and insures smooth action when the knob 39 is actuated.

Referring now more particularly to the indicator curve on the indicator plate 4|, it will be understood that the operator of the instrument sights a plane through the telescope, and operates knob 39 to move the gauge wires 49 and 50 so that the sighted plane is exactly included between them. In sighting the airplane, the handle I Il, telescope andk slotted reading plate are tilted to some position such as that shown in Fig. .4. Except for such movement as may be imparted to it by operation of knob 39, the indicator plate 4| is tilted or moved through the same angle as the slotted reading plate 29. Operation of the knob 39 to include the spotted plane exactly between the gauge wires will rock the indicator plate correspondingly, so that its net angular movement may be greater or less than the angular movement of the instrument handle and the reading plate 29. In-the position of Fig. 4 the net angular movement of the indicator plate is somewhat less than that of the reading plate. Y

For the purpose of estimating the distance and altitude of an airplane for air raid warning service, mathematical exactness is not required; it is suihcient if the distance be estimated in miles and the altitude in one of four height zones. Moreover, for spotting purposes, airplanes may be classied roughly into size groups, for example, groups having wing spreads of the order of 40 feet,\60 feet and 80 feet. With practice it is possible, on sighting an airplane through the telescope to Aclassify it as falling within one or another size group.

j For illustration, suppose it is desired to plot on the indicator plate- 4|l an indicator curve for use in the instrument in estimating the distance and altitude of an airplane in the 60 foot class.

To avoid crowding of the distance indicating lines at the far end of the scale, and facilitate estimations at the greater distance for which the instrument is calibrated, it is preferred to plot the curve by making a series of observations on an object of known width at distances corresponding to those indicatedfon the transparent scale plate i9, As before stated the mile `spaces between the vertical distance scale lines are equal. j Each indicator curve may be plotted for its width class by sighting an object of convenient "width, representing, for example, the 60 foot class, at successive distances bearing the same relation to miles as the Width of the sighted object bears to 60 feet. For example, if an object three feet wide is viewed at one twentieth of a mile through the telescope, and the knob 39 is rotated until the object is exactly included between the gauge wires, a point of the indicator curve may be plotted that represents a 60 foot wide airplane a mile away. Operation of the knob positions the indicator plate, and that portion of it visible through the narrow reading slot oppositev the 1 mile distance line on the scale is marked. Similar marks are made in a similar manner for the 1% mile point, 2 mile' point, and so on, and a continuous curve drawn throughthe marked points.

For simplicity of illustration, only one indicator curve has been shown in the drawings, but it will be understood that similar curves may be plotted for making distance and altitude estimates of objects in the 40 foot wide class, the 80 foot wideA class, and others as desired. Such a 40 foot class indicator curve would be'similar to the 60 foot class 'indicator curve, and appear above it on the indicator plate. The 80 foot class curve would be similar to the 60 foot curve land be below it on the indicator plate.

It is evident that additional 'curves may be added to give the instrument the desired degree of refinement.Y For example, there may be three curves for use with airplanes in each width class, representingv the apparent airplane width ywhen the plane is viewed head-on or directly from' the rear, sideways, and, at an intermediate angle. The utility of theinstrument as anr estimator, however, is not dependent on such refinements; for usual airplane spotting work for air raid warning service, satisfactory estimates of ldistance and altitude can be made. with only one curve for each selected airplane width class, such f as the 40, 60 and 80 foot width classes mentioned.

To insure continuance of this angular relation while estimate readings are being taken, a clamping lever 63 is pivoted at 65 in a slot provided for it in the handle plate |3. The lower end of the lever is formed with a thumb or finger piece 61, urged constantly away from the handle plate by a coil spring 68 under compression between the thumb piece and the plate. The other end 'of the lever extends inwardly of the handle plate `|3 and is provided with a clamping end 1| for In'the normal orsubstantially level position of thetilting head` ||9,"as indicated byithe dotted lines in Fig. '7, thehead'rests upon a vertical supporting pin |4l fixed on the forward part of the direction pointer |31.

As shown in Figs. 7 and 8, the direction pointer |31 is rotatable with the instrument casing overa circular disc |5| bearing compass direction markings. The disc |5| is fixed to a head '|53 secured to the sleeve |42 by a screw pin |55, whose innerV end, as shown in Fig. V'1, projects through'the sleeve and .into a neck or groove in the rotatablevertical shaft. |39 carrying the direction pointer arm |31.

Thus by loosening set screw |51 in the mounting tube |59 the entire instrument may be raised or lowered to convenient spotting height with respect to the mounting tube, and the casing l and pointer will remain in rotatable assembled relation, upon tightening the set screw.

Means are provided to prevent rotation of the sleeve |42 with respect to the mounting tube |59. As shown in Figs. 7 and 11, a fiat bar |53 has its lower end |65 fixed within the mounting tube, and its upper end projecting through a slot provided in the bottom closure |61 of the sleeve to receive the bar slidably but non-rotatably.

A bottom flange |1| is provided on the lower end of the mounting tube |59, by which the tube may be fixed to any suitable support |13 in properly oriented position of the disc |5|, which is movable vertically but non-rotatably with respect to the mounting tube, being fixed to the sleeve |42.

The operations of spotting an airplane and reading the instrument are as already described, except that in the embodiment of Fig. 1 the direction pointer is moved with respect to a fixed scale, and the long bar handle and friction grip facilitate the operations of tilting the casing and making the readings.

altitude and distance, including a transparent r scale plate pivotally and pendulously carried by the support and bearing altitude and distance markings, an opaque reading plate xedly carried by the support behind said scale plate and having a reading slot therein extending across said scale plate, an indicator plate bearing airplane size-class markings and pivotally carried by the support behind said reading plate slot, and apparent size gauging means carried by the support and connected to the indicator plate for moving it during size-gauging operation proportionately to the range.

2. An airplane spotting estimator instrument comprising a handle, means for estimating altitude and distance, including a transparent scale plate pivotally and pendulously carried by the handle and bearing altitude and distance markings, an opaque reading plate carried by the handle behind said scale plate and having a reading slot therein extending ,across'said scale plate,

an indicator plate bearing airplane size-class markingsA and pivotally carried bythe handle behind said reading plate Slot, apparent size .gauging means carried by the handle and connected to the indicator plate for moving it during size-gauging operation proportionately to the range, and direction indicating means including a rotatably supported direction disc having a handle rest to receive the instrument handle and 4angularly movable to indicate direction by horizontal angular movement of said handle.

3. An airplane spotting estimator instrument comprising a support, means carried by the support for estimating altitude and distance including a'transparent scale plate pivotally and pendulously carried by the support and bearing altitude and distance markings, an opaque reading plate iixedly carried by the support behind said `scale plate and having a reading slot therein extending across said scale plate, an indicator plate bearing airplane size-class markings and pivotally carriedby the support behind said reading plate slot, and apparent size gauging means carried bythe support vincluding a pair of gauge wires, and a gauge actuating shaft for moving said gauge wires toward and away 4from each other, said shaft being connected to the indicator plate for moving it angularly behind said reading slot during gauging operation proportionately to the range.

4. An airplane spotting estimator instrument comprising a support, means carried by the support for estimating altitude andl distance includ- ,ing a transparent scale plate pivotally and pendulously carried by the support and bearing altitude and distance markings, an opaquereading plate xedly carried by the support behind said scale plate and having a reading'slot therein extending across said scale plate, an indicator plate bearing airplane size-class markings and pivotally carried by the support behind said reading plate slot, and apparent size gauging means carried by the support including a pair of pivoted scissors bars, a gauge wire carried by each scissors bar, amanually operable gauge actuating `shaft having oppositely grooved pin-receiving portions each having a pin connected to a scissors bar for moving the gauge wires toward and from each other en rotative movement of said shaft, said shaft being connected to the indicator plate for moving it angularly behind said reading slot during gauging operation proportionately to the range.

5. An airplane spotting estimator instrument comprising a support, means carried by the support for estimating altitude and distance including a transparent scale plate pivotally and pendulously carried by the support and bearing altitude and distance markings, an opaque reading plate xedly carried by the support behind said scale plate and having a reading slot therein extending across said scale, an indicator plate bearing airplane size-class markings and pivotally carried by the support behind said reading plate slot, apparent size gauging means carried by the support including a pair of gauge wires, a gauge actuating shaft, and means controlled by the shaft for moving said gauge wires toward and away from each other, said shaft being connected to the indicator plate formoving it angularly behind said reading slot during gauging operation proportionately to the range, and a telescope carried by the support including said gauge Wires within its field of view.

6. An airplane spotting estimator instrument :comprising afsupportand means i or 4estimating altitude and-distance :including ,a v transparent scale .plate f pix/totally `aand .i pendulouslyzcarried by thesupport 'andlhavinga Weighted member main- -tainingrit in :upright ,position duringitilting ont-he gauging'means carried by lthe supportincludi-ng f a lpair-of `gauge vvires,l a manually operablagauge r"d/f'l'fuatingshaft, means. controlled by the shaft formoving saidgauge Wirestovvard and :from -eachother, said shaft being connected -tothe-indicatorplate for movi-ng it angularly :behindfsaid reading slot `dur-ing gauging Voperation K4.proportionately-to the range, and-a ftelescopeecarrfied by lthe support in iii'red angular relation thereto and including said gauge-wires within its .field of view.

flfA-nlairplane spotting estim-ator instrument comprising .a support, and means for Aesti-mating .altitude and distance including a transparent scale. plate pivotally. and,r pendulously` .carried by the support and having a weighted member maintain-ing Vit infuprightfposition during tilting oi the support, said scale plate bearing a series of altitude zone markings 'and a series of equal intervaled numerically successive distance unit markings, an opaque reading plate flxedly carried by the support behind said scale plate and having a reading slot therein extending across said scale plate, an indicator plate bearing airplane sizeclass markings and pivotally carried by the support behind said reading plate slot, apparent size gauging means carried by the support including a pair of pivoted scissors bars, each carrying one of a pair of gauge wires, a manually operable gauge actuating shaft, means controlled by the shaft for moving said gauge wires toward and from each other, said shaft being connected to the indicator plate for moving it angularly behind said reading slot during gauging operation proportionately to the range, and a telescope carried by the support in fixed angular relation thereto and including said gauge Wires Within its field of vieW.

8. An airplane spotting estimator instrument comprising a handle, and means for estimating altitude and distance including a transparent scale plate pivotally and pendulously carried by the handle and having a Weighted member maintaining it in upright position during tilting of the handle, said scale plate bearing a series of altitude zone markings and a series of equal-intervaled numerically successive distance unit markings, an .opaque reading plate iixedly carried by the handle behind said scale plate and having a reading slot therein extending across said scale plate, an. indicator plate bearing airplane size-class markings and pivotally carried by the handle behind said reading plate slot, apparent size gauging means carried by the handle including a pair of pivoted scissors bars, a gauge wire carried by each scissors bar, a manually operable gauge actuating shaft, means controlled by the shaft for rockl ing said scissors bars to move said gauge wires toward and from each other, saidl shaft being connected to the indicator plate for movingit angularly behind said reading slot during gauglli() .ing-:operation prcporltionately to mbe-ranges', iand -a' rtelescopevcarriediby :ther handle. in fxedangular relation hereto :and --.in'cluding :said l,gauge wires .within its field .fo-f wiewfandidirecticn rindicating .means :including Vfa rotatably s supper-ted direction disc, having ia handle vreet to :receive ethe .instrunient fhandie :ianid angularly, movable to yindicate directionbyhorizontalfangularmovementioisaid handle. l

.9. 4.An iairplane spotting estimator l instrument comprisingaecasingmeans carried by thecasing -for estimating :altitude .aand-.distance including a .transparent scalefplate ,pivotal-ly, and; pendulously carried lin Y)the nas-ing :and fi-bearingaltitude fand distance lian opaque ,reading gplate ixedly .carried Vthe casing ibehindssad scale .plate and nayingatreadingslot there-in extending acnoss saidfseale iplate,.iaruindicatorplate bear- .ing :airplane ssizei-class :marking-s fand ,pivotal-1y :carried :in the .casing-,behind Isaid i reading plate slot, apparent. fsine gauging means car-rind fby the nasingi ineludingia pain roffgauge wires-and -a-gauge actuating shaft and means ..controlled by the .shafft fior said gauge .wires toward .and away tromieachothersaid shaftAgeing,l connected to: the! indicator, platesiorfmoving; it angularly@ be- --said :reading :slot during 'gaugin-g Voperation .proportionately ,-tothe framgafa. tilting-headplate .supporting said easing means .for `rnairmail-ling -saidhead; plate ,inttiltedepositijomfand. means 7as,- .sociated-athereWi-thltorindioating the directionof a spotted airplane comprising a pivoted direction indicator carrying said tilting head plate, a direction disc for said pivoted indicator, and means for mounting said disc securing it against rotational movement.

10. An airplane spotting estimator instrument comprising 'a casing, means carried by the casing for estimating altitude and distance including a transparent scale plate pivotally and pendulously carried in the casing and bearing altitude and distance markings, an opaque reading plate xedly carried in the casing behind said scale plate and having a reading slot therein extending across said scale plate, an indicator plate bearing airplane size-class markings and pivotally mounted in the casing behind said reading plate slot, apparent size gauging means carried by the casing including a pair of pivoted gauge Wires, a gauge actuating shaft and means controlled by the shaft for rocking said gauge Wires toward and from each other, said shaft being connected to said indicator plate for moving it angularly behind said reading slot during gauging operation proportionately to the range, a telescope xedly mounted on the casing and including said gauge wires Within its iield of View, a tilting head plate supporting said casing, means for frictionally holding said head plate in tilted position, and,v means associated therewith for indicating the direction of a spotted airplane comprising a direction indicator carrying said tilting head plate, a vertically adjustable sleeve pivotally supporting said direction indicator, means for guiding said sleeve in vertical, rectilinear non-rotative movement, means for securing said sleeve in vertically adjusted position, and a direction disc having compass markings xedly carried by said sleeve below said direction indicator.

11. An airplane spotting estimator instrument comprising a casing, means for estimating altitude and distance including a transparent scale plate pivotally and pendulously carried in the casing and having a Weighted member maintaining it in upright position during tilting of the casing, said scale plate bearing a series of altitude zone marklings and a series of equal-intervaled numerically successive distance unit markings, an opaque reading plate iixedly mounted in the casing behind said scale plate and having a reading slot therein extending across said scale plate, an indicator plate bearing a series of diierent airplane size-class markings and pivotally carried in the casing behind said reading plate slot, apparent size gauging means carried by the casing including a' pair of pivoted scissors bars, each carrying one of a pair of pivoted gauge Wires, a manually operable gauge actuating shaft and means controlled by the shaft for moving said gauge wires toward and away from each other, said shaft being connected to the indicator plate for moving it angularly behind said` reading slot during gauging operation proportionately to the range, a telescope carried by the casing in fixed angular relation therewith and including said gauge Wires Within its field of vieW, a tilting head plate supporting said casing, means for indicating the direction of a spotted airplane including a direction indicator having `bearings for tiltably mounting and frictionally holding said tilting head plate, a vertically adjustable sleeve pivotally supporting said direction indicator and xedly carrying a direction marked disc in proximity thereto, means for guiding said sleeve in vertical rectilineary non-rotative movement, and means for securing said sleeve in vertically adjusted position.

'reading s1otthe1"ein extending racross s'aidscale plate, an indicator plate bearing a'- series of Iairplane size-class markingslpivotally mounted-in the casing behind saidv readingplate slot, Amanu-` ally-operable apparent. size-gauging means icarried by the casing and connected tothe indicator plate for moving it during gauging operation proportionately to thev range,"aJ telescope -x'edly mounted on the casing and'including said sizegauging meansfwithin its eldvof viev'v, a tilting headrfor supporting-said casing, means for indicating the direction of a spottedl airplane including a direction indicator having bearingsfor tilt ably mounting and frictionally holding said tilting head, a shaft member rockably mounted in said bearings and having said tilting head xed thereto, a bar handle for rocking said shaft to tilt the head and casing, means pivotally supporting said indicator and a direction marked disc fixedly carried thereby in proximity to said indicator.

CHARLES SADOWSKY. 

